diff --git a/Gemfile b/Gemfile
index 498b06c..abc0e6a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,7 +12,7 @@ gem 'slim-rails'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3', '~> 1.3.6'
 # Use Puma as the app server
-gem 'puma', '~> 3.12'
+gem 'puma', '~> 4.3'
 
 # sass-rails -> sassc
 gem 'sassc-rails'
diff --git a/Gemfile.lock b/Gemfile.lock
index 12112ca..ba06772 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -138,7 +138,9 @@ GEM
       mimemagic (~> 0.3.2)
     memoist (0.16.2)
     method_source (1.0.0)
-    mimemagic (0.3.5)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
     minitest (5.14.1)
@@ -150,7 +152,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     os (1.1.0)
     public_suffix (4.0.5)
-    puma (3.12.6)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.2.2)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -268,7 +271,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   jquery-rails
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (= 6.0.3.1)
   ridgepole
   sassc-rails